Eliminating or reducing vibrations is an important consideration in the design and operation of various objects. Objects ranging from the very small, such as micro-electronics, to the very large, such as buildings, are susceptible to undesired vibrations. If not ameliorated, these vibrations can cause negative effects, such as damage to the object. Accordingly, many modern objects include vibration dampers to reduce undesired vibrations.
A tuned mass damper is a common form of vibration damper and includes a mass that is specifically designed, or tuned, to oscillate at a frequency that counteracts an undesired vibration in an object. When the tuned mass damper is attached to the vibrating object, kinetic energy is dynamically transferred from the vibrating object to the moving mass within the damper to reduce the amplitude of the undesired vibration of the object.
Devices that capture mechanical energy from the environment and convert it to a more useful form are known as energy harvesters. Some vibration dampers act as energy harvesters by converting vibrational energy into electricity that can be stored or used to power other devices. A device that combines the functions of a vibration damper and an energy harvester is commonly known as a vibration energy harvesting damper (“VEHD”).
A known example of a VEHD is shown in FIG. 1 and generally identified by reference character 120. The VEHD 120 is attached to an object 122 that is subjected to an external periodic force F(t), which causes the object to vibrate along the vertical axis over time. The external force F(t) comprises one or more harmonic force components that can be presented mathematically by a Fourier series. The first mode of these harmonic force components are typically the only harmonics large enough to cause concern and are therefore of particular importance. The frequency of this first mode harmonic is denoted by ω.
A casing 124 of the VEHD 120 is formed of non-magnetic material and is secured to the vibrating object 122. The casing 124 and the object have a combined mass denoted by m1 and oscillate rectilinearly with displacement x1(t), as a result of the force F(t). Within the casing 124, the VEHD 120 includes a spring 126, a tuned mass 128, a magnet 130 and an electrically conductive coil 132. The spring 126 is connected between the casing 124 and the tuned mass 128 and has a stiffness coefficient denoted by c1 and some dissipative (viscous) coefficient. The tuned mass 128 and the magnet 130 are connected together and retained within the casing 124. Together, the tuned mass 128 and the magnet 130 have a combined mass denoted by m2 and oscillate rectilinearly with displacement x2(t). The coil 132 is secured within the casing 124 (such as by embedding the coil 132 in the casing 124) and is positioned so that it surrounds the magnet 130.
When properly designed, the spring 126, the tuned mass 128 and the magnet 130 oscillate to suppress the vibrations of the object 122 and act as the tuned mass damper in the VEHD 120. At the same time, the movement of the magnet 130 causes a changing magnetic flux through the coil 132, which induces a current in the coil 132 that can be used to power other devices. In this way, the coil 132 and the magnet 130 act as the energy harvester in the VEHD 120. The minimal amplitude of the movement of the vibrating object 122, and the maximal amplitude of the movement of the tuned mass 128 and magnet 130, may be achieved when c1/m2=ω2. However, the current induced in the coil 132 is correlated to the movement of the magnet 130 alone, and will generally be maximized when the movement of the magnet 130 has a phase shift of 90 degrees from the movement of the coil 132. Accordingly, it could be said that only a portion of the amplitude of the movement of the tuned mass 128 and the magnet 130 goes to electricity generation. Thus, it is necessary to balance efficiency between the vibration damping and the energy harvesting functions of the VEHD 120. Additionally, the efficiency of the VEHD 120 will be impacted by variations in the frequency ω of the external force F(t).
U.S. Pat. No. 7,345,372 entitled “Electromechanical Generator for, and Method of, Converting Mechanical Vibrational Energy into Electrical Energy,” and U.S. Pat. No. 7,453,163 entitled “Electromechanical Generator for, and Method of, Converting Mechanical Vibrational Energy into Electrical Energy” disclose an electromechanical device using a resonant mass-spring arrangement mounted within an enclosure. The resonant mass-spring arrangement comprises an inertial mass mounted to an internal wall of the enclosure by a spring and a damper, the spring and damper being in a parallel configuration. These references show that including a damper causes additional resistance and leads to additional losses of effectiveness of the device.
U.S. Pat. No. 7,554,224 entitled “Electromechanical Generator for Converting Mechanical Vibrational Energy into Electrical Energy” discloses further improvements to the electromechanical devices disclosed in U.S. Pat. Nos. 7,345,372 and 7,453,163.
U.S. Pat. No. 7,586,220 entitled “Electromechanical Generator for Converting Mechanical Vibrational Energy into Electrical Energy” discloses further improvements to the electromechanical devices disclosed in U.S. Pat. No. 7,554,224, focusing in particular on the magnetic core assembly.
U.S. Pat. No. 7,999,402 entitled “Electromechanical Generator for Converting Mechanical Vibrational Energy into Electrical Energy” discloses further improvements to the electromechanical devices disclosed U.S. Pat. Nos. 7,345,372 and 7,453,163, including incorporating at least one spring and the vibratable mount being connected to the resonator support for mounting the resonator to a vibratable body from which electrical energy is to be harvested.
U.S. Pat. No. 9,595,893 entitled “Non-stationary Multi-frequency Vibration Energy Harvesting with Tunable Electrical Impedance” discloses a simple mass-spring-damper model packed by elaborated electronics.
U.S. Pat. No. 9,461,530 entitled “Electromechanical Generator for Converting Mechanical Vibrational Energy into Electrical Energy” discloses an electromechanical generator based on a simple mechanical model comprising a housing, an electrically conductive coil assembly fixedly mounted in the housing, a magnetic core assembly movably mounted in the housing for linear vibrational motion along an axis, a first biasing device, mounted between the housing and the magnetic core assembly, adapted to apply a centering force acting to oppose movement of the magnetic core assembly away from a central position on the linear axis and a second magnetic biasing device adapted to provide a compensating force to compensate for variations in the centering force of the first biasing device due to temperature.
U.S. Pat. No. 9,121,233 entitled “Mitigation of Downhole Component Vibration using Electromagnetic Vibration Reduction” discloses an apparatus for reducing vibration in a downhole component. The apparatus includes: an electrically conductive auxiliary mass attached to the component and configured to vibrate in a direction corresponding to a direction of downhole component vibration and reduce a portion of the downhole component vibration; and a magnetic component configured to generate a magnetic field through the auxiliary mass having a direction at least partially perpendicular to the direction of auxiliary mass vibration, the magnetic field configured to induce a current in the auxiliary mass in response to auxiliary mass vibration. The apparatus has an auxiliary mass vibration frequency tuned relative to a selected natural vibration frequency of the downhole component to reduce vibration of the downhole component, the auxiliary mass vibration frequency based on a magnetic stiffness of the auxiliary mass, the magnetic stiffness based on a strength of the magnetic field and/or a resistance of the auxiliary mass.
U.S. Pat. No. 8,866,316 entitled “Tunable Vibration Energy Harvester and Method” discloses an energy harvester that comprises an energy conversion device configured to convert vibrational energy to electrical energy, a mass coupled to the energy conversion device, and at least one biasing mechanism coupled to the mass. The biasing mechanism is selectively adjustable and selectively adjusting the biasing mechanism adjusts a resonance frequency of the energy conversion device and the mass.
U.S. Pat. No. 8,866,317 entitled “Broadband Vibrational Energy Harvesting” discloses a system that converts environmental vibrational energy into electrical energy consisting of a transducer that undergoes oscillating movement in response to the vibrational energy in order to produce an oscillating electrical signal. Power electronics process the oscillating electrical signal. A control system (including at least one control element of the power electronics, at least one sensor and control electronics) carries out a control scheme that dynamically varies the dampening of the oscillating movement of the transducer over time. The control scheme is based upon a predetermined parametric relation involving a plurality of variables derived from the properties measured by the at least one sensor. In several embodiments, the plurality of variables includes a first variable representing excitation frequency of the transducer.
U.S. Pat. No. 8,253,281 entitled “Energy Harvesting Apparatus Incorporated into Shock Absorber” discloses a simple model based on a vehicle shock absorber applicable for deployment on a vehicle.
U.S. Pat. No. 8,222,754 entitled “Vibration-Based Power Generator” discloses a vibration-based power generator with variable stiffness oscillator connected to a base. The oscillator comprises an inertial mass moving relative to the base in response to vibrations. The oscillator has a neutral position corresponding to a position of the oscillator when no vibrations are transmitted to the base. The oscillator has a first position where the mass is at a first distance and a second position where the inertial mass is at a second distance from a position of the mass when the oscillator is in neutral position. The second distance is greater than the first distance. A stiffness of the oscillator at the second position is greater than a stiffness of the oscillator at the first position. A transducer generating electric power in response to movement of the inertial mass is associated with the oscillator.
U.S. Pat. No. 8,063,498 entitled “Harvesting Energy from Vehicular Vibrations” discloses an energy harvesting apparatus deployed on a vehicle and that comprises a vehicular shock absorber capable of reciprocating translational movement in response to roadway perturbations. A coil is mounted within the shock absorber. An engine is also mounted within the shock absorber for converting the translational movement into rotational movement. A magnet is coupled to the engine and is configured to be rotated in the vicinity of the coil to produce electrical energy in the coil.
U.S. Pat. No. 9,484,795 entitled “Vibration Energy Harvesting Using Cycloidal Motion” discloses an energy conversion apparatus, comprising: a casing; an electromagnetic (EM) transducer disposed at one side of the casing; a round magnet disposed in the casing and free to move relative to the casing and the EM transducer in at least two degrees of freedom; and a ferromagnetic object fixed relative to the casing at an opposite side of the casing to the EM transducer and arranged to attract the magnet toward a neutral position within the casing. The EM transducer is positioned so that movement of the magnet relative to the EM transducer varies the magnetic field through the EM transducer, thereby generating electrical potential across at least a part of the EM transducer.
U.S. Pat. No. 7,569,952 entitled “High Efficiency, Inductive Vibration Energy Harvester” discloses an energy harvester focusing on magnetic properties. The apparatus comprises a permanent magnet magnetic field source (should have two dipole magnets) attached by a pair of compact spiral disk springs to an induction coil. The springs position the magnet so that the induction coil surrounds one end of the magnet where the flux density is greatest. In addition, the magnetic flux emerging from that end of the magnet is enhanced by a disk of magnetic material having high permeability and high flux density.
U.S. Pat. No. 9,887,610 entitled “Flexible Devices, Systems, and Methods for Harvesting Energy” discloses a microfluidic device comprising: a channel configured to be pressurized; a fluid contained within the channel; one or more chambers in fluid communication with the channel; a flexible membrane configured to deform in response to a force applied thereto, thereby pressurizing the fluid; a plurality of magnetic elements separated from one another by nonmagnetic spacers, wherein the pressurized fluid is capable of moving the plurality of magnetic elements and the nonmagnetic spacers along the channel; and a plurality of coils surrounding the channel, the coils comprising an electrically conductive material. Also disclosed is a microfluidic device comprising: a channel configured to be pressurized; a fluid contained within the channel; one or more chambers in fluid communication with the channel; a plurality of magnetic elements separated from one another by nonmagnetic spacers, wherein the fluid is capable of moving the plurality of magnetic elements and the nonmagnetic spacers along the channel; and a plurality of coils surrounding the channel, the coils comprising an electrically conductive material, wherein the one or more chambers comprise a first chamber and a second chamber, and the first chamber has a smaller cross-sectional area than the second chamber. Further disclosed is a system comprising: a plurality of chambers; a plurality of channels connected to the plurality of chambers and forming fluid interconnection therebetween; a fluid located in the plurality of chambers and in the plurality of channels; a plurality of pistons sized and configured to pressurize the fluid in the plurality of chambers; a plurality of coils surrounding the plurality of channels; a plurality of magnetic elements located in the plurality of channels, the magnetic elements being sized and configured to induce current in the plurality of coils; and a plurality of nonmagnetic spacers located in the plurality of channels and separating one magnetic element from another.
U.S. Pat. No. 9,835,218 entitled “Vehicle Active Damper” discloses a device which includes a damping actuator that is provided between a radiator and a vehicle body so as to be interposed in a substantially vertical direction, and a coupling member that elastically couples between the vehicle body and an engine. The damping actuator is formed from an elastic modulus-variable member having an elastic modulus that varies according to the strength of an applied magnetic field. The coupling member transmits vibrations of the engine to the vehicle body along a substantially vertical direction.
U.S. Pat. No. 9,726,254 entitled “Tuned Mass Damper” discloses a tuned mass vibration damper including at least one damper mass and at least one guide component part to movably guide the at least one damper mass.
U.S. Pat. No. 8,914,154 entitled “Active Tuned Vibration Absorber” discloses an actuator, several combinations of springs and a control system for a tuned mass damper.
U.S. Pat. No. 7,461,728 entitled “Active Vibration Damping System” discloses an actuator and control system for an active vibration damper.
U.S. Pat. No. 5,564,537 entitled “Adaptive-Passive Vibration Control System” discloses an apparatus containing a springing mass damper and an electronic controller designed to instruct the actuator to adapt the mass (for instance by fluid) to compensate for the sensed vibration. Also the stiffness of the spring, rather than the mass of the weight, may be adjusted on-line to “tune” the vibration absorber. Further, if more than one excitation frequency is present, a plurality of on-line adaptive and/or purely passive vibration absorbers may be cascaded so as to minimize vibrations due to a plurality of excitation frequencies.
U.S. Pat. No. 4,724,923 entitled “Vibration Absorber with Controllable Resonance Frequency” discloses an apparatus comprising an electromagnet rigidly connected to the first part of the structure and a body of magnetizable material connected via a resilient element to the first part of the structure, while an air gap is provided between the electromagnet and the body. The electromagnet is energized by a variable current through at least one coil and it exerts an attractive force on the body which is oscillating due to the vibrations occurring in the first part of the structure. The restoring force exerted by the resilient element on the secondary body has the effect of lowering the resonant frequency of the second body on the resilient element as compared to the resonant frequency of the apparatus when no current passes through the coil. The amount of this lowering can be controlled depending upon the frequency of the exciting vibration by varying the electric current through the coil.
U.S. Pat. No. 9,871,472 entitled “Energy-Harvesting Apparatus with Plural Mechanical Amplifiers” discloses an energy-harvesting device containing a first mechanical amplifier responsive to the input vibration and a second mechanical amplifier coupled to the first mechanical amplifier. At least one of the first and second mechanical amplifiers comprises a parametric resonator, and a power output of the energy harvester is generated by damping the second mechanical amplifier.
U.S. Pat. No. 9,787,220 entitled “Energy Harvester” discloses a very simple apparatus with a mass and first and second elastic beams connecting the mass to the frame, wherein the first and second elastic beams are provided with opposite stiffnesses so that the mass experiences a preselected stiffness in a predefined range of conditions.
U.S. Pat. No. 9,748,872 entitled “Vibrational Energy Harvesting System” discloses a very simple vibrating system furnished by elaborate control and energy generating schemes.
U.S. Pat. No. 9,653,980 entitled “Energy Harvesting System Using Several Energy Sources” discloses using several energy sources and paying attention to electromagnetic issues.
U.S. Pat. No. 9,644,601 entitled “Linear Faraday induction Generator for the Generation of Electrical Power from Ocean Wave Kinetic Energy and Arrangements Thereof” discloses a linear faraday induction generator for the generation of electrical power from ocean wave kinetic energy, and arrangements thereof focusing on large-scale solutions.
U.S. Pat. No. 9,627,925 entitled “Methods and. Apparatus for Managing and Utilizing Harvested Energy” discloses process or flow diagrams for a specific energy harvester.
U.S. Pat. No. 9,121,394 entitled “Energy Harvester for Converting Vibrational Motion of a Vibrating Equipment into Electrical Energy, and a Device for Monitoring the Operation of a Vibrating Equipment” discloses a device having a mechanical scheme based on a pendulum arranged to be pivotably attached to vibrating equipment.
U.S. Pat. No. 9,118,187 entitled “Vibrational Energy Harvester” discloses a mass-cantilever energy harvester.
U.S. Pat. No. 9,059,628 entitled “Energy Harvesting” discloses devices applicable in vehicles vibrating with low frequencies.
U.S. Pat. No. 8,987,924 entitled “Self-tuning Energy Harvester” discloses an apparatus for generating electricity containing a flexural member configured to flex upon being subject to a vibration. A plurality of weight displacement systems is disposed at the flexural member, each weight displacement system in the plurality being configured to displace a moveable weight upon receipt of a signal. A processor is configured to provide a signal to each weight displacement system in order to achieve a desired resonant frequency of the flexural member. An electricity generating device is coupled to the flexural member and configured to generate electricity upon flexing of the flexural member. This apparatus is applicable for logging tools conveyed through boreholes penetrating geologic formations.
U.S. Pat. No. 8,350,394 entitled “Energy Harvester Apparatus Having improved Efficiency” discloses a system consisting of more springs and masses, representing 2 and 3 degrees-of-freedom (DOF) energy harvesters, in which some collidable mass elements move ballistically along a linear path defined by a guiding rod, and at the same time produce electricity in the electromagnetic module.
U.S. Pat. No. 9,871,472 entitled “Energy-Harvesting Apparatus with Plural Mechanical Amplifiers” discloses a device using the effect of parametric resonance. The energy harvester comprises a first mechanical amplifier responsive to the input vibration and a second mechanical amplifier connected to the first mechanical amplifier. At least one of the amplifiers comprises a parametric resonator, and a power output of the energy harvester is generated by damping the second mechanical amplifier.
U.S. Pat. No. 7,464,800 entitled “Torsional Vibration Damper of a Rotating Shaft” discloses a vibration energy harvesting tuned damper applied for rotational systems.
Although the contributions of the above references are laudable, these known devices may not provide both efficient energy harvesting and efficient vibration damping, particularly when the frequency of an object's vibrations are changing over a broad range. Accordingly, improvements and alternatives for vibration energy harvesting dampers are generally desired.